When the iPhone 4 was released in June of 2010, it was not without it's share of glitches. The first reported glitch was with the iPhone 4's wireless 3G antenna. This was suspected to cause poor reception and a high volume of dropped calls. The next reported issue was with the iPhone 4's proxy sensor. Apple addressed this problem on the software level, with the release of iOS 4.1.

Since the iOS 4.1 release, there have been many questions as to whether or not the update resolved the iPhone 4 proxy sensor issue once and for all. From my own experience, I have not had any complaints since this software update was made public.

Some of you may be wondering, "What in the world is a proxy sensor is and what function does it serve?" Without getting too involved, every iPhone (including the original iPhone 2G, 3G and 3GS models) have a ratio sensor. This sensor emits an infrared (IR) light that detects the presence of a solid object (such as a head or hand), while you have a call in progress, or while you are listening to a voicemail. When it detects a solid object, it turns your iPhone's LCD panel off. This is a function you'll probably never miss until it's no longer working.

The function of the proxy sensor actually has two distinct advantages. First, you are not muting your phone, accidently pushing buttons, or hanging up on your callers with your cheek. The other advantage is that it preserves power consumption and improves your phone's battery life in between charging cycles.

As an Apple Certified Macintosh Technician who makes a living supporting and fixing Apple products, this is an issue that could not be ignored. The reputation of my business hung in the balance of being able to find a reliable and professional solution for this problem. I've done extensive research and testing on this topic and feel like I've made a significant headway in resolving this annoying glitch ..

In the four years that I've been repairing iPhones, it's only been recently that I've been experiencing the problems that have been widely documented and reported. Since the release of iOS 4.1, I have not seen any cases in which the iPhone's proxy sensor malfunctioned on a phone that had not been modified. When I say "modified" I mean a phone that has undergone a color conversion, or one that the front glass and LCD had been replaced due to the phone being dropped and having the original glass broken. I noticed that the occurrence was more after after a color conversions had been performed.

Since the proxy sensor on the iPhone 4 is located on the iPhone's mid-frame and is not a part of the front glass and LCD assembly, I had never questioned the quality of the parts I was purchasing. With that in mind, I began testing every phone prior to repair. I wanted to be sure that the phones were functioning properly, prior to repairs, or color conversions being made. So far, I have yet to find one that was not working just fine before the repair. It turns out, the problem was attributed to two factors.

1. The unique sensitivity of each iPhones proxy sensor.
2. The proxy sensor cover on some of the replacement glass is not tinted as dark. This allows too much light to pass through.

I've read over many articles and blogs that suggest using black tape with holes punched out, or a black magic marker to cover the iPhone's proxy sensor. I did not feel that either of these fixes offered a professional solution, or one that I would even be proud to employ in my practice.

After speaking with my parts distributor, I found the best solution for this problem is an inexpensive "sensor cover." This cover is a small piece of film with a coating that looks to be the same red polarized coating on some sunglasses. This small piece of film is installed over the top of the iPhone's proxy sensor.

At the end of the day, it would appear that too much light is getting in and confusing the phone. The proxy sensor cover filters excess light from entering the phone and there by solves the problem.